x86/asm: Make serialize() always_inline

In order to allow serialize() to be used from noinstr code, make it
__always_inline.

Fixes: 0ef8047 ("x86/static-call: provide a way to do very early static-call updates")
Closes: https://lore.kernel.org/oe-kbuild-all/202412181756.aJvzih2K-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241218100918.22167-1-jgross@suse.com

Author: jgross1

arch/x86/include/asm/special_insns.h

@@ -217,7 +217,7 @@ static inline int write_user_shstk_64(u64 __user *addr, u64 val)
 
 #define nop() asm volatile ("nop")
 
-static inline void serialize(void)
+static __always_inline void serialize(void)
 {
 	/* Instruction opcode for SERIALIZE; supported in binutils >= 2.35. */
 	asm volatile(".byte 0xf, 0x1, 0xe8" ::: "memory");